IMO, the tax report really isn't very useful as it only arranges data by Form > Payee. The payee generally doesn't matter, at least not when actually filling out the tax forms.
What is relevant for filling out taxes is the Form > Line item. Since we already have assigned tax form lines to the Simplifi categories, that information is available.
What is needed is the option to list the tax report by Form > Line Item > Category. That would make the report actually useful.